1. Field of the Invention
The present invention relates to an A-D converter for use in an electronic balance.
2. Prior Art
A conventional high precision electronic balance takes a fairly long time to complete one measurement of weight, because of a slow response of the high-resolving A-D converter which is necessarily used in an electronic balance. In general, the longer the response time of an A-D converter becomes, the higher is its resolving power and the larger is its converting capacity. Such being the case, it takes a very long time, especially when it is necessary for the balance to average a number of sampled weight values due to a noisy condition of weighing an object to be measured. Certainly, there is known a high-resolving and high-speed A-D converter in which a D-A converter of a weighted-resistance type is incorporated. However, such an A-D converter has a disadvantage that the D-A converter incorporated therein, which requires many high-precision resistors, is temperature-sensitive, and therefore, liable to be unstable unless provided with a special temperature controlling means. Fine adjustment and preparation of the precision resistors are also troublesome.